I'm pretty sure you can use any of the following PS's to test the 840AV on the bench:

IIcx, IIci, IIsi, IIvi, IIvx, Q700, C650, Q650, Q800, PM7100, PM8100.

I may be mistaken, but as I understand it, the Q650 and the Q800 are the same circuit board with slight clock multiplier resistor and gestalt resistor differences. So power supplies for one should work in the other, and by the transitive property, the rest follow. But I may be misremembering something....